Development of an Augmented Reality system using ARToolKit

Development of an Augmented Reality system using ARToolKit and user invisible markers
4.1.1 Ink Pen
Now will be described in more detail the properties of the before mentioned ink. The
ink is invisible to ultraviolet light and the human eye. Ultraviolet light is below 400nm.
The human eye can see light between 400nm and 750nm. The ink emits 840nm
frequency light and has a 793nm absorption frequency, which lies in the IR range. There
exist three classifications for IR light, near-IR, mid-IR and far-IR. This classification is
based on ascending light frequencies. The ink fits into the near-IR spectrum, 750nm to
3000nm. The light spectrum is graphically displayed in Figure 4.4.
Figure 4.4 The light spectrum
The ink itself is delivered in the form of an ink pen, the so called IR1PenSM. The tip of
the pen is green fluorescent to the human eye. The manufacturer of the ink notifies that
the ink is influenced by ultraviolet light. Estimated is that the ink will last for about a
week, but keeping it out of ultraviolet light will increase this period. The manufacturer
mentions a price of $18,43. This is without handling costs, administration costs and
shipping costs. The pen is displayed in Figure 4.5.
Figure 4.5 IR1PenSM
Anything written on white paper can not be seen by the human eye. But, when viewed
with a modified camera with IR functionality the ink becomes visible. An external light
source is not required. This is being shown in Figure 4.6 and Figure 4.7.
Figure 4.6 Image as seen by the human eye Figure 4.7 Image captured by IR camera
4.1.2 IR Powder
Not only the manufacturer delivers ink that is visible in the infrared range, but it also
has at its disposal powder with similar properties, the so called IRDC2. This IR
fluorescent powder is visible at both 880nm and 1050nm. Therefore it needs to be
stimulated by an external light source, that produces either blue or red light, of
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